watch: strip watch flags from NODE_OPTIONS in child process

[marcopiraccini]

When NODE_OPTIONS contains --watch, the watch mode parent process spawns a child that inherits the same NODE_OPTIONS, causing the child to also enter watch mode and spawn another child, creating an infinite loop of process spawning.

This PR strips watch-related flags (--watch, --watch-path,--watch-preserve-output, --watch-kill-signal) from NODE_OPTIONS before passing the environment to the child process. This mirrors the existing logic that already strips these flags from process.execArgv.

Non-watch flags in NODE_OPTIONS (e.g., --max-old-space-size) are preserved.

Fixes: #61740

This is actually similar to #61838 but more "surgical", it just avoid propagating watch flags.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.65%. Comparing base (3725bd2) to head (bb649d4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62143      +/-   ##
==========================================
- Coverage   89.65%   89.65%   -0.01%     
==========================================
  Files         676      676              
  Lines      206543   206543              
  Branches    39547    39548       +1     
==========================================
- Hits       185184   185178       -6     
- Misses      13480    13487       +7     
+ Partials     7879     7878       -1     

see 28 files with indirect coverage changes

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